xf86-video-armada + etnaviv (Was: Re: I.MX6 HDMI support in v4.2)

[Russell King - ARM Linux]

On Mon, Sep 28, 2015 at 04:48:08PM +0200, Lucas Stach wrote:
> I've looked at that again and the issue here seems to be that GStreamer
> is handing us a pointer to a buffer that isn't aligned to a page. The
> buffers size is properly rounded up to a pagesize, as requested by
> QueryImageAttributes, but if the buffer start pointer isn't aligned to a
> page boundary we end up with an non-mappable buffer anyway.
> 
> Unfortunately there is no obvious way for a driver to request a minimum
> alignment for the buffer. The only possible fix is for the client to
> always align the buffer to a page boundary in hopes that this is enough
> for the hardware to map it directly and allow to skip any unwanted
> copying.

We can't just "round up" the size.  We've no idea whether the buffer
came from shmem (for XvShmPutImage), or whether it's part of an internal
X buffer (for XvPutImage).  In the latter case, we've no idea whether
data in the remainder of the page will be read or written by the CPU
when, eg, a signal occurs - and X does use signals.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.